Allow anonymous access to registry

plugin.go

@@ -74,13 +74,13 @@ func mainfestToolPath() string {
 func (p *Plugin) Exec() error {
 	args := []string{}
 
-	if p.Config.Username == "" {
+	if p.Config.Username == "" && p.Config.Password != "" {
 		return errors.New("you must provide a username")
 	} else {
 		args = append(args, fmt.Sprintf("--username=%s", p.Config.Username))
 	}
 
-	if p.Config.Password == "" {
+	if p.Config.Password == "" && p.Config.Username != "" {
 		return errors.New("you must provide a password")
 	} else {
 		args = append(args, fmt.Sprintf("--password=%s", p.Config.Password))